Adhesive composition for polarizer, adhesive film comprising same, polarizing film comprising same and display divice comprising polarizing film

Abstract

The present application relates to an adhesive composition for a polarizing plate, an adhesive film comprising the same, a polarizing film comprising the same, and a display device comprising a polarizing film.

Description

Technology Field

[0001] The present application relates to an adhesive composition for a polarizing plate, an adhesive film comprising the same, a polarizing film comprising the same, and a display device comprising a polarizing film. Background Technology

[0002] Building on recent advancements in optical technology, display devices utilizing various methods—such as plasma display panels (PDPs), liquid crystal displays (LCDs), and organic light-emitting diodes (OLEDs)—are being proposed and marketed to replace conventional cathode ray tubes. Recently, the characteristics required for these display devices have been becoming increasingly sophisticated, and consequently, the requirements for peripheral components applied to these devices, such as optical films and polarizing films, are also becoming more advanced.

[0003] Liquid crystal displays are utilized in various display devices such as TVs, mobile phones, car navigation systems, portable game consoles, and other portable terminals, taking advantage of features such as low power consumption, low-voltage operation, lightweight design, and thin profile. Examples of these liquid crystal displays include VA (Vertical Alignment) mode, IPS (In-Plane Switching) mode, FFS (Fringe Field Switching) mode, and OCB (Optical Compensated Bend) mode. These liquid crystal displays generally consist of a backlight, a liquid crystal cell containing liquid crystal molecules sandwiched between two electrodes, and two polarizing plates provided on each side of the liquid crystal cell. When voltage is applied, transmitted light is controlled by a change in the optical refractive index of the liquid crystal molecules to display an image. Furthermore, in these modes, the light absorption axes of the two polarizing films are arranged at 90° to each other so that light is not transmitted when no voltage is applied to the liquid crystal cell (when no voltage is applied). A liquid crystal display that displays a black color when a low voltage is applied and a white color when a voltage is applied is called a normal black type.

[0004] Recently, efforts are being made in the polarizer market to minimize defects and increase product productivity. Previously, moisture-permeable substrates (WVRT > 200 g / m²) were used as protective materials for polarizers. 2 Polarizers have traditionally been manufactured using water-based adhesives with TAC (Triacetyl cellulose) having a water vapor resistance of 1 / 200 g / m²; however, currently, non-permeable substrates (WVRT < 200 g / m²) such as PET, acrylic, or COP films are used. 2 ·day) is also mainly used.

[0005] When using conventional breathable protective substrates, it was possible to attach the upper and lower protective substrates of the polarizer with a single type of adhesive. However, in product lines that use both breathable and non-breathable substrates simultaneously, rather than using only breathable substrates as is common recently, a problem has arisen in that it is difficult to achieve sufficient adhesive strength using only a single type of water-based adhesive.

[0006] In other words, adhesive compositions that adhere well to breathable protective substrates have poor adhesion to non-breathable substrates, and similarly, adhesive compositions that adhere well to non-breathable protective substrates have poor adhesion to breathable substrates. Furthermore, with the recent emergence of various protective substrates and the application of diverse characteristics such as difficult-to-bond substrates, adhesives inevitably vary depending on the substrate. Therefore, research is required on adhesives that can be applied to both breathable and non-breathable substrates by improving the adhesion margin.

[0007] Currently, to address this issue, it is becoming common practice to apply adhesives to polarizers separately on the top and bottom surfaces, tailored to moisture-permeable, moisture-impermeable, and non-adhesive substrates. However, while using separate adhesives for moisture-permeable, moisture-impermeable, and non-adhesive substrates offers the advantage of improved adhesion, it necessitates replacing the adhesive for each product line, leading to increased costs and reduced product productivity.

[0008] When the adhesive applied to the polarizing film is replaced, it typically takes about 3 to 6 hours of time to change the path due to wet / dry switching, and additional time is required for adhesive discharge / filling, mesh roll replacement, pipe cleaning / washing, etc.

[0009] Therefore, it is necessary to develop an adhesive layer for polarizers that can be used regardless of the type of protective substrate (breathable, non-breathable, or difficult-to-attach) attached to the polarizer, tailored to currently applied product lines. Prior art literature

[0010] Japanese Registered Patent Publication 6536022 The problem to be solved

[0011] The present application relates to an adhesive composition for a polarizing plate, an adhesive film comprising the same, a polarizing film comprising the same, and a display device comprising a polarizing film. means of solving the problem

[0012] One embodiment of the present specification provides an adhesive composition for a polarizing plate comprising a polymer comprising: a monomer (a) having two allyl groups as functional groups; and a monomer (b) having a thiol group as a functional group, wherein the monomer (a) having two allyl groups as functional groups is present in an amount of 30 parts by weight or more and 50 parts by weight or less based on 100 parts by weight of the polymer.

[0013] In another embodiment, an adhesive film comprising an adhesive composition for a polarizing plate according to the present application or a cured product thereof is provided.

[0014] In another embodiment, a polarizing film is provided comprising: a polarizer; a first adhesive layer and a second adhesive layer provided on both sides of the polarizer; a first transparent protective film provided on the opposite side of the first adhesive layer that contacts the polarizer; and a second transparent protective film provided on the opposite side of the second adhesive layer that contacts the polarizer; wherein the first adhesive layer and the second adhesive layer are adhesive films according to the present application.

[0015] Finally, a display device comprising a polarizing film according to the present application is provided. Effects of the invention

[0016] An adhesive composition for a polarizing plate according to one embodiment of the present invention comprises a polymer comprising a monomer (a) having two allyl groups as functional groups and a monomer (b) having a thiol group as a functional group, wherein the monomer (a) having two allyl groups as functional groups satisfies an amount of 30 parts by weight or more and 50 parts by weight or less based on 100 parts by weight of the polymer.

[0017] Accordingly, it is characterized by excellent adhesion regardless of moisture permeability, moisture non-permeability, or recently developed non-adhesive transparent protective films, and by introducing an Ene-thiol reaction system unlike the crosslinking system of existing adhesive compositions to improve both flexibility and adhesion compared to existing ones, particularly improving adhesion to non-adhesive transparent protective films.

[0018] In other words, both flexibility and adhesion can be improved compared to crosslinking by the existing acrylic curing system, and due to step-growth crosslinking instead of chain-growth, the gel reaction is slow but shrinkage is low and crosslinking density is favorable, so it has the characteristic of particularly improving adhesion.

[0019] Ultimately, the adhesive layer containing this has excellent wetting properties on the polarizer or substrate and excellent adhesion, resulting in the polarizing film containing it having excellent appearance quality. Brief explanation of the drawing

[0020] FIG. 1 is a diagram showing a laminated structure of a polarizing film according to one embodiment of the present specification. Specific details for implementing the invention

[0021] Before describing the present invention, we will first define some terms.

[0022] In this specification, when a part is described as "comprising" a certain component, this means that, unless specifically stated otherwise, it does not exclude other components but may include additional components.

[0023] In this specification, 'p to q' means a range of 'p or more and q or less'.

[0024] In this specification, acrylate means that it includes both acrylate and (meth)acrylate.

[0025] Hereinafter, the present invention will be described in detail with reference to the drawings so that those skilled in the art can easily practice the present invention. However, the present invention may be embodied in various different forms and is not limited to the description below.

[0026] One embodiment of the present specification provides an adhesive composition for a polarizing plate comprising a polymer comprising: a monomer (a) having two allyl groups as functional groups; and a monomer (b) having a thiol group as a functional group, wherein the monomer (a) having two allyl groups as functional groups is present in an amount of 30 parts by weight or more and 50 parts by weight or less based on 100 parts by weight of the polymer.

[0027] The present invention satisfies the composition and content of the adhesive composition for polarizing plates as described above, thereby improving both flexibility and adhesion compared to crosslinking by the conventional acrylic curing system. Furthermore, due to step-growth crosslinking rather than chain-growth, the gel reaction is slow, but shrinkage is low and crosslinking density is favorable, resulting in particularly improved adhesion.

[0028] The characteristics of each adhesive composition included in this application are described below.

[0029] In one embodiment of the present application, the polymer comprises a monomer (a) having two allyl groups as functional groups; and a monomer (b) having a thiol group as a functional group.

[0030] At this time, the polymer may have a polymeric form in which the above monomer is bonded.

[0031] In one embodiment of the present application, the monomer (a) comprising two allyl groups as functional groups may be used without limitation as long as it comprises two allyl groups, and may further comprise functional groups other than additional allyl groups.

[0032] At this time, the functional group may include one or more selected from the group consisting of a carboxyl group, an epoxy group, an ester group, a thiol group, an alcohol group, and an ether group.

[0033] In one embodiment of the present application, the monomer (a) comprising two allyl groups as functional groups may further comprise two or more ester groups.

[0034] In one embodiment of the present application, the monomer (a) comprising two allyl groups as functional groups is not particularly limited, but examples include diallyl maleate, diallyl adipate, diallyl phthalate, glycerin diallyl ether, trimethylolpropane diallyl ether, pentaerythritol diallyl ether, etc. The monomer (a) comprising two allyl groups as functional groups may be used alone or two or more types may be used in combination.

[0035] In one embodiment of the present application, the monomer (a) comprising two allyl groups as functional groups may preferably be diallyl phthalate.

[0036] In one embodiment of the present application, the monomer (b) having a thiol group as the functional group is not particularly limited, but may have two or more thiol groups in one molecule, and is not particularly limited, examples include aliphatic polythiol compounds such as ethanedithiol, propanedithiol, hexamethylenedithiol, decamethylenedithiol, tolylene-2,4-dithiol; aromatic polythiol compounds such as xylenedithiol; polythiol compounds such as diglyl dimercaptan, triglycol dimercaptan, tetraglycol dimercaptan, thiodiglycol dimercaptan, thiotriglycol dimercaptan, thiotetraglycol dimercaptan, trimethylolpropane tris-β-mercaptopropionate; and polythiol compounds having one or more dithian rings in one molecule, such as 2,5-dimercaptomethyl-1,4-dithian. The monomers (b) having these thiol groups may be used alone or in combination of two or more types.

[0037] In one embodiment of the present application, the polymer may further comprise a monofunctional acrylate or a polyfunctional acrylate.

[0038] In one embodiment of the present application, the monofunctional acrylate may be an alkyl (meth) acrylate. In the alkyl (meth) acrylate, the alkyl group may be branched even in a straight chain if it has three or more carbon atoms. Specific examples of alkyl (meth) acrylates include methyl (meth) acrylate, ethyl (meth) acrylate, isopropyl (meth) acrylate, butyl (meth) acrylate, isobutyl (meth) acrylate, tert-butyl (meth) acrylate, etc. In addition, alkyl (meth)acrylates with a higher number of carbon atoms in the alkyl group, such as 2-ethylhexyl (meth)acrylate; aralkyl (meth)acrylates, such as benzyl (meth)acrylate; (meth)acrylates of terpene alcohols, such as isobornyl (meth)acrylate; (meth)acrylates having a tetrahydrofurfuryl structure, such as tetrahydrofurfuryl (meth)acrylate; (meth)acrylates having a cycloalkyl group in the alkyl group, such as cyclohexylmethyl methacrylate, dicyclofentanyl acrylate, and 1,4-cyclohexanedimethanol monoacrylate; aminoalkyl (meth)acrylates, such as N,N-dimethylaminoethyl (meth)acrylate; and (meth)acrylates having an ether bond in the alcohol group, such as 2-phenoxyethyl (meth)acrylate, ethyl carbitol (meth)acrylate, and phenoxypolyethylene glycol (meth)acrylate, It can be used as a monosynthetic monomer.

[0039] In addition, monofunctional (meth)acrylates having a hydroxyl group in the alcohol portion or monofunctional (meth)acrylates having a carboxyl group in the alcohol portion can also be used. Specific examples of monofunctional (meth)acrylates having a hydroxyl group in the alcohol portion include 2-hydroxyethyl (meth)acrylate, 2- or 3-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 2-hydroxy-3-phenoxypropyl (meth)acrylate, trimethylolpropane mono(meth)acrylate, pentaerythritol mono(meth)acrylate, etc. Specific examples of monofunctional (meth)acrylates having a carboxyl group in the alcohol portion include 2-carboxyethyl (meth)acrylate, 1-[2-(meth)acryloyloxyethyl]phthalic acid, 1-[2-(meth)acryloyloxyethyl]hexahydrophthalic acid, 1-[2-(meth)acryloyloxyethyl]succinic acid, and 4-[2-(meth)acryloyloxyethyl]trimellitic acid.

[0040] In another embodiment, the monofunctional acrylate may be 4-hydroxybutyl acrylate (4-HBA).

[0041] The above term "monofunctional acrylate" refers to an acrylate having one functional group within the molecule, and the functional group may be an acrylate group.

[0042] In one embodiment of the present application, one type of monofunctional acrylate may be used.

[0043] In one embodiment of the present application, two types of monofunctional acrylates may be used.

[0044] In one embodiment of the present application, the polyfunctional acrylate refers to an acrylate having two or more functional groups within the molecule, and the functional group may be an acrylate group.

[0045] In one embodiment of the present application, the number of functional groups of the polyfunctional acrylate may be 2 or more and 10 or less, preferably 2 or more and 6 or less, and more preferably 2 or more and 5 or less.

[0046] The above polyfunctional acrylate can be expressed differently as a difunctional acrylate when it has two functional groups, and as a trifunctional acrylate when it has three functional groups.

[0047] In one embodiment of the present application, representative examples of difunctional acrylates include alkylene glycol di(meth)acrylates, polyoxyalkylene glycol di(meth)acrylates, di(meth)acrylates of halogen-substituted alkylene glycols, di(meth)acrylates of aliphatic polyols, di(meth)acrylates of hydrogenated dicyclopentadiene or tricyclodecane dialkanols, di(meth)acrylates of dioxane glycol or dioxane dialkanols, di(meth)acrylates of alkylene oxide adducts of bisphenol A or bisphenol F, and epoxy di(meth)acrylates of bisphenol A or bisphenol F.

[0048] In one embodiment of the present application, more specific examples of difunctional acrylates include ethylene glycol di(meth)acrylate, 1,3-butanediol (meth)acrylate, 1,4-butanediol (meth)acrylate, 1,6-hexanediol di(meth)acrylate, 1,9-nonanediol di(meth)acrylate, neopentyl glycol di(meth)acrylate, trimethylolpropane di(meth)acrylate, pentaerythritol di(meth)acrylate, ditrimethylolpropane di(meth)acrylate, diethylene glycol di(meth)acrylate, triethylene glycol di(meth)acrylate, dipropylene glycol di(meth)acrylate, tripropylene glycol di(meth)acrylate, polydiethylene glycol di(meth)acrylate, polypropylene glycol di(meth)acrylate, polytetramethylene glycol di(meth)acrylate, and hydroxypivaric acid Di(meth)acrylate of neopentyl glycol ester, 2,2-bis[4-{2-(2-(meth)acryloyloxyethoxy)ethoxy}phenyl]propane, 2,2-bis[4-{2-(2-(meth)acryloyloxyethoxy)ethoxy}cyclohexyl]propane, hydrogenated dicyclopentadienyl di(meth)acrylate, tricyclodecanedimethanol di(meth)acrylate, 1,3-dioxane-2,5-diyl di(meth)acrylate [alias: dioxane glycol di(meth)acrylate], di(meth)acrylate of acetalate of hydroxypivalaldehyde and trimethylolpropane [chemical name: 2-(2-hydroxy-1,1-dimethylethyl)-5-ethyl-5-hydroxymethyl-1,3-dioxane], There are di(meth)acrylates of 1,3,5-tris(2-hydroxyethyl)isocyanurate, etc.

[0049] In one embodiment of the present application, a representative example of a polyfunctional acrylate with three or more functions is a poly(meth)acrylate of an aliphatic polyol with three or more valence. Specific examples include glycerin tri(meth)acrylate, trimethylolpropane tri(meth)acrylate, ditrimethylolpropane tri(meth)acrylate, ditrimethylolpropane tetra(meth)acrylate, pentaerythritol tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, dipentaerythritol tetra(meth)acrylate, dipentaerythritol penta(meth)acrylate, dipentaerythritol hexa(meth)acrylate, glycerin ethylene oxide modified tri(meth)acrylate, ethylene oxide modified trimethylolpropane tri(meth)acrylate, etc.

[0050] Meanwhile, acrylate oligomers include urethane (meth)acrylate oligomers, polyester (meth)acrylate oligomers, and epoxy (meth)acrylate oligomers.

[0051] In one embodiment of the present application, the polyfunctional acrylate may be hydroxypivalic acid neopentylglycol diacrylate; or tris(2-hydroxyethyl)isocyanurate triacrylate.

[0052] In one embodiment of the present application, one type of polyfunctional acrylate may be used.

[0053] In one embodiment of the present application, two types of polyfunctional acrylates may be used.

[0054] In one embodiment of the present application, an adhesive composition for a polarizing plate is provided, wherein the monomer (a) comprising two allyl groups as functional groups is present in an amount of 30 parts by weight or more and 50 parts by weight or less, based on 100 parts by weight of the polymer.

[0055] In addition, in one embodiment of the present application, an adhesive composition for a polarizing plate is provided in which the monomer (b) having a thiol group as a functional group is 50 parts by weight or more and 70 parts by weight or less, based on 100 parts by weight of the polymer.

[0056] By including a polymer satisfying the above composition and content, the adhesive composition according to the present invention can exhibit adhesive strength regardless of moisture permeability, moisture impermeability, or recently developed non-adhesive transparent protective films. In other words, unlike the crosslinking system of conventional adhesive compositions, an Ene-thiol reaction system is introduced to improve both flexibility and adhesive strength compared to existing methods, thereby particularly improving adhesion to non-adhesive transparent protective films.

[0057] In one embodiment of the present application, the adhesive composition for a polarizing plate further comprises a radical initiator.

[0058] In the present application, the radical initiator may be one capable of initiating the polymerization of the polymerizable monomer and the polymerizable monomer by irradiation with ultraviolet light, and a conventionally known one may be used. Specific examples of radical initiators include acetophenone-based initiators such as acetophenone, 3-methylacetophenone, benzyldimethylketal, 1-(4-isopropylphenyl)-2-hydroxy-2-methylpropan-1-one, 2-methyl-1-[4-(methylthio)phenyl-2-morpholinopropan-1-one and 2-hydroxy-2-methyl-1-phenylpropan-1-one; benzophenone-based initiators such as benzophenone, 4-chlorobenzophenone and 4,4'-diaminobenzophenone; benzoin ether-based initiators such as benzoin propyl ether and benzoin ethyl ether; thioxantone-based initiators such as 4-isopropylthioxantone; and others such as xantone, fluorenone, camphorquinone, benzaldehyde, anthraquinone, etc.

[0059] In one embodiment of the present application, the adhesive composition for a polarizing plate comprises the radical initiator in an amount of 5 parts by weight or less based on 100 parts by weight of the adhesive composition for a polarizing plate.

[0060] In another embodiment, the radical initiator may be included in an amount of 5 parts by weight or less, preferably 4 parts by weight or less, more preferably 3 parts by weight or less, based on 100 parts by weight of the adhesive composition for the polarizer, and specifically 0.1 parts by weight or more, preferably 1 part by weight or more.

[0061] In one embodiment of the present application, an adhesive film comprising an adhesive composition for a polarizing plate according to the present application or a cured product thereof is provided.

[0062] The method for preparing the adhesive composition for a polarizing plate according to the present application is not particularly limited and can be obtained by mixing the above components. An appropriate organic solvent may also be used to adjust the viscosity. There are no particular limitations on the mixing method, and the mixture may be sufficiently stirred and mixed at room temperature (20°C or higher and 25°C or lower) in a room shielded from UV light so that curing does not proceed, until the liquid becomes uniform.

[0063] When applying the above adhesive composition for the polarizing plate, it may be applied to either the transparent protective film or the polarizer, or to both.

[0064] The above adhesive film can be laminated onto a substrate film during manufacturing.

[0065] In one embodiment of the present application, the adhesive film may include the adhesive composition according to one embodiment of the present application as is.

[0066] In one embodiment of the present application, the adhesive sheet may include a cured product of an adhesive composition according to one embodiment of the present application.

[0067] In one embodiment of the present application, the substrate film may be selected from the group consisting of PET (polyethylene terephthalate), polyester, PC (polycarbonate), PI (polyimide), PEN (polyethylene naphthalate), PEEK (polyether ether ketone), PAR (polyarylate), PCO (polycylicolefin), polynorbornene, PES (polyether sulfone), and COP (cycloolefin polymer).

[0068] In another embodiment, the film described above may be PET (polyethylene terephthalate).

[0069] In one embodiment of the present application, the thickness of the substrate film is 10 μm or more and 200 μm or more. It may be less than or equal to, preferably 15 μm or more and 100 μm or less, and more preferably 20 μm or more and 75 μm or less.

[0070] In addition, it is preferable that the above-mentioned substrate film be transparent. The meaning of the substrate film being transparent as described here is that the light transmittance of visible light (400~700 nm) is 80% or more.

[0071] In one embodiment of the present application, an adhesive film is provided that further comprises a release film on one or both sides of the adhesive film.

[0072] In one embodiment of the present application, the thickness of the adhesive film is 0.1 μm or more and 300 μm or more. It may be less than.

[0073] In another embodiment, the thickness of the adhesive film is 0.1 μm or more and 100 μm or more. Less than, 0.1 µm or more, 80 µm Less than, 0.1 µm or more and 50 µm It may be less than.

[0074] In one embodiment of the present specification, the thickness of the adhesive film is preferably greater than 0 μm and less than or equal to 20 μm, greater than 0 μm and less than or equal to 10 μm, preferably 0.1 μm to 10 μm or 0.1 μm to 5 μm. As the thickness of the adhesive film satisfies the above range, the uniformity and adhesive strength of the adhesive film are excellent, and the appearance of the polarizing plate can be prevented.

[0075] The thickness of the adhesive film is not particularly limited by the method of applying the adhesive composition containing solids in the solution of the adhesive film, and various means such as direct dripping of the adhesive composition, roll coating, spraying, and immersion can be employed.

[0076] In one embodiment of the present application, the adhesive film may have a surface energy of 35 mN / m or less.

[0077] In one embodiment of the present application, the adhesive film may have a surface water contact angle of 70° or more.

[0078] In one embodiment of the present application, the adhesive film may have a surface energy of 35 mN / m or less, a surface energy of 30 N / m or less, a surface energy of 25 mN / m or less, and may satisfy a surface energy of 5 mN / m or more.

[0079] In one embodiment of the present application, the adhesive film may have a surface water contact angle of 70° or more, a surface water contact angle of 100° or more, a surface water contact angle of 110° or more, and may satisfy a range of 180° or less.

[0080] An adhesive film according to one embodiment of the present application satisfies the above surface water contact angle and surface energy, and as the UV-curing adhesive composition includes monofunctional and polyfunctional acrylates of a specific composition and content, it satisfies the above range and has the characteristic of excellent spreadability with a substrate.

[0081] In another embodiment, a polarizing film comprising: a polarizer; a first adhesive layer and a second adhesive layer provided on both sides of the polarizer; a first transparent protective film provided on the side of the first adhesive layer opposite to the side in contact with the polarizer; and a second transparent protective film provided on the side of the second adhesive layer opposite to the side in contact with the polarizer; wherein the moisture permeability of the first transparent protective film and the second transparent protective film is 150 g / m² 2 The present invention provides a polarizing film having a duration of 24hr or less, wherein the first adhesive layer and the second adhesive layer are adhesive films according to the present application.

[0082] In one embodiment of the present application, the moisture permeability of the first transparent protective film and the second transparent protective film is 150 g / m²2 It may be less than / 24hr, specifically 145g / m² 2 / 24hr or less, more specifically 140g / m² 2 It may be less than / 24hr, and 10g / m² 2 / 24hr or more, 20 g / m² 2 It can satisfy a range of / 24hr or more.

[0083] In one embodiment of the present application, the polarizing film can be manufactured by applying an adhesive composition for a polarizing plate onto the polarizer, and then bonding the polarizer and a transparent protective film using a roll laminator or the like.

[0084] Specifically, after the above bonding, ultraviolet light is irradiated onto a polarizing plate to cure the adhesive composition. The source of the ultraviolet light is not particularly limited, but a low-pressure mercury lamp, a medium-pressure mercury lamp, a high-pressure mercury lamp, an ultra-high-pressure mercury lamp, a chemical lamp, a black light lamp, a microwave-excited mercury lamp, a metal halide lamp, etc., having a light emission distribution at a wavelength of 400 nm or less, may be used. The amount of ultraviolet irradiation (integrated light amount) is not particularly limited, but it is preferable that the amount of ultraviolet irradiation in the wavelength range effective for activating the polymerization initiator is 100 mJ / cm2 or more and 2,000 mJ / cm2 or less. Within this range, the reaction time is appropriate, and it is possible to prevent deterioration of the adhesive layer itself or the polarizing film due to heat radiated from the lamp and heat generation during polymerization.

[0085] The above polarizing film is stored at room temperature (20°C or higher and 25°C or lower; specifically, 25°C) for a period of 16 hours or more and 30 hours or less immediately after UV irradiation. The polarizing film can be manufactured by the completion of curing.

[0086] In one embodiment of the present application, the transparent protective film material is preferably a material having excellent transparency, mechanical strength, thermal stability, moisture barrier properties, isotropy, etc. Examples include cellulose resins such as cellulose diacetate and cellulose triacetate, polyester resins such as polyethylene terephthalate and polyethylene naphthalate, acrylic resins such as polymethyl methacrylate (PMMA), polystyrene resins such as polystyrene or acrylonitrile-styrene copolymer (AS resin), polyolefin resins such as polycarbonate resin, polyethylene, polypropylene, ethylene-propylene copolymer, and cycloolefin polymer, polyvinyl chloride resin, polyamide resins such as nylon or aromatic polyamide, polyimide resin, polysulfone resin, polyethersulfone resin, polyetheretherketone resin, polyphenylene sulfide resin, polyvinyl alcohol resin, polyvinylidene chloride resin, polyvinyl butyral resin, polyarylate resin, polyoxymethylene resin, epoxy resin, or blends of these resins.

[0087] In one embodiment of the present application, cellulose resins may include cellulose triacetate (TAC), cellulose diacetate, cellulose tripropionate, cellulose dipropionate, etc. Among these, cellulose triacetate, cycloolefin polymer, polyethylene terephthalate, or acrylic resin are preferred from the perspective of availability and cost, and cycloolefin polymer, polyethylene terephthalate, or acrylic resin are more preferred from the perspective of availability and moisture permeability. If the moisture permeability of the protective film is high, moisture may pass through the protective film and easily enter the polarizer side, which may lead to a risk of deterioration in the quality of the polarizer.

[0088] A polarizer exhibits the characteristic of being able to extract only light vibrating in one direction from incident light vibrating in multiple directions. This characteristic can be achieved by stretching polyvinyl alcohol (PVA) that has absorbed iodine under strong tension. For example, more specifically, a polarizer can be formed by passing through a swelling step in which a PVA film is immersed in an aqueous solution to swell; a step of dyeing the swollen PVA film with a dichroic substance that imparts polarization; a stretching step in which the dyed PVA film is stretched to align the dichroic dye substances parallel in the stretching direction; and a complementary color step in which the color of the PVA film that has undergone the stretching step is corrected. However, the polarizer of the present invention is not limited thereto.

[0089] The above polarizer may be a polarizer well known in the art, for example, a film made of polyvinyl alcohol (PVA) containing iodine or a dichroic dye. The above polarizer may be manufactured by dyeing iodine or a dichroic dye onto a polyvinyl alcohol-based film, but the method of manufacturing thereof is not particularly limited. A polarizing film refers to a state comprising a polarizer and a protective film.

[0090] The above polarizer is manufactured by undergoing the following processes: a process of uniaxially stretching a polyvinyl alcohol-based resin film; a process of dyeing the polyvinyl alcohol-based resin film with a dichromatic dye and adsorbing the dichromatic dye; a process of treating the polyvinyl alcohol-based resin film with the adsorbed dichromatic dye with an aqueous boric acid solution; a process of washing with water after treatment with the aqueous boric acid solution; and a process of bonding a protective film to the uniaxially stretched polyvinyl alcohol-based resin film in which the dichromatic dye is adsorbed and oriented after these processes are carried out.

[0091] The above uniaxial stretching may be performed before dyeing with a dichromatic dye, simultaneously with dyeing with a dichromatic dye, or after dyeing with a dichromatic dye. When uniaxial stretching is performed after dyeing with a dichromatic dye, this uniaxial stretching may be performed before or during boric acid treatment. Furthermore, it is also possible to perform uniaxial stretching at multiple of these stages. To perform uniaxial stretching, the material may be stretched uniaxially between rolls with different peripheral speeds, or stretched uniaxially using a heat roll. Additionally, it may be dry stretching performed in the atmosphere, or wet stretching performed in a state swollen by a solvent. The stretching ratio is not particularly limited, but is typically 4 to 8 times.

[0092] Meanwhile, the thickness of the polarizer is preferably 5㎛ to 40㎛, and more preferably 5㎛ to 25㎛. When the thickness of the polarizer satisfies the above numerical range, the optical properties are excellent, and the amount of polarizer shrinkage in a low-temperature state is appropriate, so the entire polarizer has excellent thermal durability.

[0093] In addition, when the above polarizer is a polyvinyl alcohol-based film, the polyvinyl alcohol-based film may be used without special restrictions as long as it contains a polyvinyl alcohol resin or a derivative thereof. In this case, derivatives of the polyvinyl alcohol resin include polyvinyl formal resin and polyvinyl acetal resin, but are not limited thereto. Furthermore, commercially available polyvinyl alcohol-based films, such as Kuraray’s P30, PE30, PE60, and Nippon Synthetic’s M2000, M3000, M6000, etc., may be used, but are not limited thereto.

[0094] The above polyvinyl alcohol-based film preferably has a degree of polymerization of 1,000 to 10,000, and more preferably 1,500 to 5,000. When the degree of polymerization satisfies the above numerical range, the movement of molecules is free, and it can be flexibly mixed with iodine or dichroic dyes, etc.

[0095] In one embodiment of the present application, a polarizing film is provided having an adhesive strength of 150 gf / inch or more on the surface of the first adhesive layer in contact with the polarizer and the surface of the second adhesive layer in contact with the polarizer.

[0096] In another embodiment, a polarizing film is provided in which the surface of the first adhesive layer in contact with the polarizer; and the surface of the second adhesive layer in contact with the polarizer have an adhesive strength of 150 gf / inch or more, preferably 200 gf / inch or more, and 600 gf / inch or less, more preferably 400 gf / inch or less.

[0097] That is, in the polarizing film according to the present application, a first protective film is used on the upper side of the polarizer and a second protective film is used on the lower side of the polarizer; even when a non-moisture-permeable, moisture-permeable, or non-adhesive substrate is used on the upper or lower side, the adhesive composition for a polarizing plate according to the present application has a certain composition and content, thereby possessing the characteristic of excellent adhesion as described above.

[0098] FIG. 1 shows a laminated structure of a polarizing film according to one embodiment of the present application. Specifically, it can be seen that a first adhesive layer (4) and a second adhesive layer (2) are provided on both sides of a polarizer (3), and a first transparent protective film (5) and a second transparent protective film (1) with a moisture permeability are included on the upper side of each.

[0099] Figure 1 is merely one example, and the types of protective materials that may be placed on the upper and lower parts of the polarizer are not limited thereto.

[0100] In one embodiment of the present application, a polarizing film is provided in which the first adhesive layer and the second adhesive layer are the same.

[0101] In other words, unlike the conventional method of using various types of adhesives while simultaneously using moisture-permeable and moisture-nonpermeable substrates in the polarizer, the use of a single type of adhesive layer results in excellent productivity of the polarizing film and prevents cost increases associated with adhesive replacement.

[0102] The adhesive composition for a polarizer according to the present application can be suitably used in polarizers (polarizing films), phase difference films, elliptical polarizing films, anti-reflective films, brightness enhancement films, indium tin oxide sputtered transparent conductive films (ITO films), various electronics-related film components or protective films, etc. Among these, it is preferred to use it in polarizers (polarizing films).

[0103] Finally, a display device comprising a polarizing film according to the present application is provided.

[0104] The present application will be described in more detail below through embodiments according to the present application and comparative examples not according to the present application, but the scope of the present application is not limited by the embodiments presented below.

[0105] <Experimental Example>

[0106] Adhesive compositions having the composition and content of Table 1 below were each prepared.

[0107] Subsequently, the adhesive composition was applied to both sides of a polarizer (manufactured by Nippon Synthetic Co., Ltd.), a non-adhesive film (KONICA, Sanuqui film) was laminated as the first transparent protective film and Dongwoo’s W-acryl as the second transparent protective film, and then bonded using a roll laminator.

[0108] Afterwards, ultraviolet light was irradiated onto a polarizing plate to cure the adhesive composition. The source of the ultraviolet light is not particularly limited, but a low-pressure mercury lamp, an intermediate-pressure mercury lamp, a high-pressure mercury lamp, an ultra-high-pressure mercury lamp, a chemical lamp, a black light lamp, a microwave-excited mercury lamp, a metal halide lamp, etc., having a light emission distribution at a wavelength of 400 nm or less were used.

[0109] Irradiance (cumulative light intensity) is 2000 mJ / cm² 2 To achieve this, the adhesive composition for the polarizer was cured by irradiating it with ultraviolet light of a wavelength of 365 nm, thereby bonding the polarizer and the release protective film together, and a polarizer sample was prepared by cutting it to a size of 2 cm in width * 15 cm in length. At this time, for each adhesive composition for the polarizer, the release protective film was pretreated with KOH.

[0110] The polarizing film was stored at room temperature (20°C or higher and 25°C or lower; specifically, 25°C) for a period of 16 hours or more and 30 hours or less immediately after UV irradiation. The polarizing film was obtained upon completion of curing.

[0111] Acrylate Silane coupling agent cation initiator photosensitizer A monomer containing three allyl groups as functional groups A monomer containing one allyl group as a functional group Monomer (a) containing two allyl groups as functional groups Monomer (b) having a thiol group as a functional group radical initiator 4-HBA M210 M370 KBM-403 Omnicat 250 DETX Triallyl isocyanurate Ally glycidyl ether Diallyly phthalate Thiol PE1 TPO Example 1 - - - - - - - - 50 50 2 Example 2 - - - - - - - - 40 60 2 Example 3 - - - - - - - - 30 70 2 Comparative Example 1 - - - - - - - - 60 40 2 Comparative Example 2 - - - - - - - - 20 80 2 Comparative Example 3 - - - - 2 2 - - 60 40 - Comparative Example 4 - - - - - - - - 60 40Thiol BD1 2 Comparative Example 5 - - - - - - - 60 - 40 2 6 in comparison - - - - - - 30 30 - 40 2 Comparative Example 7 - - - - 2 2 30 30 - 40 Comparative Example 8 - - - - - - 60 - - 40 2 Comparative Example 9 16 50 16 15 2 2 - - - - -

[0112] The numbers in Table 1 above may represent weight parts included in the total adhesive composition. Specifically, in Table 1 above, the respective content parts are indicated based on 100 weight parts of a monomer including an acrylate, a silane coupling agent, a monomer having one to three allyl groups as functional groups, or a monomer having a thiol group as a functional group, and the cationic initiator, photosensitizer, and radical initiator are indicated based on 100 weight parts of the total adhesive composition.

[0113] At this time, the monomer may contain additional additives, and the content of the additives was not included in Table 1 above.

[0114] In Table 1 above, 4-HBA (OSAKA Chemical) used 4-hydroxybutyl acrylate, M210 (Miwon Commercial) used Hydroxypivalic Acid Neopentylglycol Diacrylate, M370 (Miwon Commercial) used tris(2-hydroxyethyl)isocyanurate triacrylate, KBM-403 (Shin-Etsu) used 3-glycidoxypropyl trimethoxysilane, a substance having an epoxy group in which at least one of the epoxy groups is a dicyclic epoxy group, Omnicat250 used (4-methylphenyl)[4-(2-methylpropyl)phenyl]-hexafluorophosphate(1-)in propylene carbonate, and DETX (IHT) used 2,4-diethylthioxantone.

[0115] In addition, in Table 1 above, Triallyl isocyanurate was TCI's I0279, Ally glycidyl ether was TCI's A0221, and Diallyly phthalate was TCI's P0290. In addition, Thiol PE1 used net(3-ameganate) iron terephthalate ([3-(3-sulfanylbutanoyloxy)-2,2-bis(3-sulfanylbutanoyloxymethyl)propyl] 3-sulfanylbutanoate) from SHOWA DENKO, Thiol BD1 used 1,4-bis(3-mercaptobutylyloxy)butane (1,4-bis(3-mercaptobutylyloxy)butane) from SHOWA DENKO, and TPO used ethyl(2,4,6-trimethylbenzoyl)phenyl phosphinate from IGM.

[0116] The polarizing film prepared above was evaluated in Experimental Examples 1 and 2 below, and the results are shown in Table 2.

[0117] Adhesion (gf / 20mm) Curing speed Hardening phenomenon Protective material SANUQI Wolf ZT COP Example 1 ◎ O O - No problem Example 2 ◎ O ◎ 20s No problem Example 3 ◎ ◎ ◎ - Sticky release interface Comparative Example 1 O X △ - No problem Comparative Example 2 - - - - Uncured Comparative Example 3 X X X No problem Comparative Example 4 - - - - Uncured Comparative Example 5 - - - Uncured Uncured Comparative Example 6 - - - - Uncured Comparative Example 7 - - - - Uncured Comparative Example 8 Compatibility issues arose Unevaluable formulation X - Comparative Example 9 X X X - No problem

[0118] <Experimental Example 1: Protective Film Adhesion Test>

[0119] The protective film for peeling was peeled off by more than 3 cm at a peeling speed of 0.5 cm / sec, and the peeling force was measured three times to calculate the average value. An XT Plus Texture Analyzer (manufactured by TA) was used for the above peeling force measurement.

[0120] At this time, the peel strength (gf / 20mm) was evaluated as ◎ if it was 200gf / 20mm or more, O if it was 120gf / 20mm or more and less than 200gf / 20mm, Δ if it was 100gf / 20mm or more and less than 120gf / 20mm, and X if it was less than 100gf / 20mm.

[0121] <Experimental Example 2: Curing Rate>

[0122] Irradiance (cumulative light intensity) is 2000 mJ / cm² 2 To this end, the adhesive composition for the polarizing plate was cured by irradiating it with ultraviolet light of a wavelength of 365 nm. Immediately after peeling off the protective film, the cured film was rubbed with a hand to check for any slippage of the film.

[0123] The curing speed was evaluated as O if it was 10 seconds or less, O if it was 10 seconds or more and 20 seconds or less, Δ if it was 20 seconds or more and 50 seconds or less, and X if it was 50 seconds or more.

[0124] As can be seen in Tables 1 and 2 above, when comparing Examples 1 to 3 with Comparative Examples 1 and 2, it was confirmed that the adhesion to non-adhering substrates was excellent when the ratio of the monomer of the present invention was satisfied. However, it was confirmed that when the respective ratios were deviated from, as in Comparative Examples 1 and 2, problems such as reduced adhesion to non-adhering substrates or incomplete curing occurred.

[0125] In the case of Comparative Example 3, a cationic initiator was used, and it was confirmed that there was a significant decrease in adhesive strength compared to the use of a radical initiator.

[0126] In the case of Comparative Examples 5 to 7, through comparative evaluation of allyl monomers, it was confirmed that the adhesive strength was inferior when using monofunctional and trifunctional allyl monomers compared to when using difunctional allyl monomers. This is because the reaction rate of monofunctional allyl monomers is unfavorable compared to other allyl monomers, resulting in incomplete curing. Additionally, it was confirmed that the adhesive strength decreased when monofunctional and trifunctional allyl monomers were mixed (Comparative Example 6).

[0127] In other words, the composition according to the present invention exhibits excellent adhesion regardless of moisture permeability, moisture impermeability, or recently developed non-adhesive transparent protective films. Unlike the crosslinking system of existing adhesive compositions, it was confirmed that by introducing an Ene-thiol reaction system, both flexibility and adhesion are improved compared to existing ones, particularly improving adhesion to non-adhesive transparent protective films. Specifically, it was confirmed that both flexibility and adhesion can be improved compared to crosslinking by the existing acrylic curing system, and that due to step-growth crosslinking rather than chain-growth, the gel reaction is slow but shrinkage is low and crosslinking density is favorable, resulting in particularly improved adhesion. Explanation of the symbols

[0128] 1: Second transparent protective film 2: Second adhesive layer 3: Polarizer 4: First adhesive layer 5: 1st transparent protective film

Claims

Claim 1 An adhesive composition for a polarizing plate comprising a polymer including a monomer (a) having two allyl groups as functional groups; and a monomer (b) having a thiol group as a functional group, wherein the monomer (a) having two allyl groups as functional groups further includes two or more ester groups, and the monomer (a) having two allyl groups as functional groups is present in an amount of 30 parts by weight or more and 50 parts by weight or less based on 100 parts by weight of the polymer, and the monomer (b) having a thiol group as a functional group is [3-(3-sulfanylbutanoyloxy)-2,2-bis(3-sulfanylbutanoyloxymethyl)propyl] 3-sulfanylbutanoate. Claim 2 An adhesive composition for a polarizing plate according to claim 1, wherein the monomer (b) having a thiol group as a functional group is 50 parts by weight or more and 70 parts by weight or less, based on 100 parts by weight of the polymer. Claim 3 An adhesive composition for a polarizing plate according to claim 1, wherein the adhesive composition for the polarizing plate further comprises a radical initiator. Claim 4 An adhesive composition for a polarizing plate according to claim 3, wherein the radical initiator is included in an amount of 5 parts by weight or less based on 100 parts by weight of the adhesive composition for a polarizing plate. Claim 5 delete Claim 6 An adhesive film comprising an adhesive composition for a polarizer according to any one of claims 1 to 4 or a cured product thereof. Claim 7 An adhesive film according to claim 6, further comprising a release film on one or both sides of the adhesive film. Claim 8 In claim 6, the thickness of the adhesive film is 0.1 μm or more and 300 μm or more. An adhesive film that is less than or equal to the following. Claim 9 A polarizing film comprising: a polarizer; a first adhesive layer and a second adhesive layer provided on both sides of the polarizer; a first transparent protective film provided on the side of the first adhesive layer opposite to the side in contact with the polarizer; and a second transparent protective film provided on the side of the second adhesive layer opposite to the side in contact with the polarizer; wherein the moisture permeability of the first transparent protective film and the second transparent protective film is 150 g / m² 2 A polarizing film having a duration of 24hr or less, wherein the first adhesive layer and the second adhesive layer are adhesive films according to claim 6. Claim 10 A polarizing film according to claim 9, wherein the surface of the first adhesive layer in contact with the polarizer; and the surface of the second adhesive layer in contact with the polarizer have an adhesive strength of 150 gf / inch or more. Claim 11 A polarizing film according to claim 9, wherein the first adhesive layer and the second adhesive layer are the same. Claim 12 A display device comprising a polarizing film according to claim 9.

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